ORIGINAL ARTICLES Center of Drug Metabolism and Pharmacokinetics, China Pharmaceutical University, Nanjing, China Berberine attenuates intestinal disaccharidases in streptozotocin-induced diabetic rats Li Liu, Yuanxiong Deng, Sen Yu, Shousi Lu, Lin Xie, Xiaodong Liu Received October 14, 2007, accepted November 23, 2007 Prof. Dr. Xiaodong Liu, Center of Drug Metabolism and Pharmacokinetics, China Pharmaceutical University, Nanjing, 210009 Jiangsu Provience P.R. China [email protected] Pharmazie 63: 384–388 (2008) doi: 10.1691/ph.2008.7778 Previous studies demonstrated anti-diabetic effects of berberine. However, the facts that berberine had low bioavailability and poor absorption through the gut wall indicated that berberine might exert its antihyperglycaemic effect in the intestinal tract before absorption. The purpose of this study was to inves- tigate whether berberine attenuates disaccharidase activities and b-glucuronidase activity in the small intestine of streptozotocin (STZ)-induced diabetic rats. Two groups of STZ-induced diabetic rats were treated with protamine zinc insulin (10 U/kg) subcutaneously twice daily and berberine (100 mg/kg) orally once daily for 4 weeks, respectively. Both age-matched normal rats and diabetic control rats received physiological saline only. Fasting blood glucose levels, body weight, intestinal disaccharidase and b-glucuronidase activities in duodenum, jejunum and ileum were assessed for changes. Our find- ings suggested that berberine treatment significantly decreases the activities of intestinal disacchari- dases and b-glucuronidase in STZ-induced diabetic rats. The results demonstrated that the inhibitory effect on intestinal disaccharidases and b-glucuronidase of berberine might be one of the mechanisms for berberine as an antihyperglycaemic agent. 1. Introduction through the gut wall (<5%) (Pan et al. 2002) indicated that berberine might exert its antihyperglycaemic effect in Carbohydrates are digested by a-glucosidase and disac- the intestinal tract before absorption. Our previous studies charidase in the small intestine. Carbohydrate digestion using Caco-2-cells showed that berberine might signifi- directly increases the postprandial blood glucose level. cantly inhibit disaccharidase activity and also showed Disaccharidases including sucrase, lactase and maltase, lo- weak inhibition of glucose absorption (Pan et al. 2002, cated on the brush border membrane, play important roles 2003). in the final digestion of carbohydrates. Diabetes mellitus The aim of the present study was to investigate whether (DM) is often associated with an increased digestion of berberine reverses disaccharidase activity in the small in- carbohydrates, protein, fat as well as absorption of glu- testine of streptozotocin (STZ)-induced diabetic rats and cose, amino acids and fatty acids. Some reports showed to explore its mechanism of action. At the same time, the hyperplasia and hypertrophy in small intestine of alloxan- enzyme b-glucuronidase, which is associated with the re- induced or streptozotocin-induced rats (Stenling et al. absorption of bile acid was also observed. 1984; Debnam et al. 1990; Zoubi et al. 1995) associated with an increase in disaccharidase activity (McAnuff- Harding et al. 2006; Adachi et al. 2003). This is to say 2. Investigations and results that an increased disaccharidase activity may be one of the reasons for high blood glucose levels. Compared with age-matched normal rats, significantly Rhizoma coptidis has been used for treating diabetes mel- higher blood glucose levels and lower body weight litus for more than one thousand years in Chinese tradi- were found in diabetic rats. Both berberine and insulin tional medicine. Berberine, a quaternary protoberberine- treatment significantly decreased blood glucose levels type alkaloid is one of the main constituents in Rhizoma and increase body weight in diabetic rats, although ber- coptidis and many other herbs. Previous studies demon- berine effect was not as good as insulin (Fig. 1). The strated anti-diabetic effects of berberine (Leng et al. 2004; results further verified antihyperglycaemic effects of ber- Tang et al. 2006; Lee et al. 2006). Berberine had been de- berine. monstrated to be beneficial by lowering blood glucose, As is shown in Figs. 2–4, the activities of disacchari- modulating lipids metabolic and scavenging free radicals dases (lactase, sucrase, maltase) were significantly in- in streptozotocin-induced diabetic rats (Tang et al. 2006). creased in the duodenum, jejunum and ileum regions of However, the facts that berberine showed low bioavailabil- small intestine in diabetic rats when compared with those ity (Lu et al. 2006; Sheng et al. 1993) and poor absorption in the normal control group. And the activities of disac- 384 Pharmazie 63 (2008) 5 ORIGINAL ARTICLES 400 30 300 20 Fig. 1: Change in the body weight (g) (A) and blood glu- 200 (mM/L) 10 cose (mM) (B) in STZ-induced diabetic rats after the Body Weight (g) administration of insulin (10 U/kg/day) and berber- 100 Blood Glucose Level 0 ine (100 mg/kg/day) for 4 weeks (mean Æ S.D., 0 7 14 21 28 35 0 7 14 21 28 35 ^ & n ¼ 5). Normal rats ( ), diabetic rats ( ), insulin Time (day) Time (day) treated diabetic rats (~) and berberine treated dia- betic rats (*). Insulin and berberine were treated to (A) (B) diabetic rats from 7th day to 35th day Fig. 4: Maltase activity in the small intestine in different treatment of rats. Fig. 2: Lactase activity in the small intestine in different treatment of rats. Each bar represents the mean Æ S.D., n ¼ 5, for each region of the Each bar represents the mean Æ S.D., n ¼ 5, for each region of the ** ** intestine. Denotes statistical difference compared with normal intestine. Denotes statistical difference compared with normal control rats. (p < 0.01, by ANOVA). DDenotes statistical difference < D control rats. (p 0.01, by ANOVA). Denotes statistical difference compared with diabetic rats. (p < 0.01, by ANOVA) compared with diabetic rats. (p < 0.01, by ANOVA) charidases were always higher in jejunum of diabetic rats rats had almost recovered to the same level of normal than that in duodenum and ileum regions of diabetic control rats. rats. The activity of lactase in duodenum, jejunum and Figure 5 shows the changes on intestinal b-glucuronidase ileum regions of diabetic rats was 4.1-fold, 1.6-fold and activity in four different treated groups of rats. The activ- 5.4-fold that in normal rats, respectively. The activity of ity of intestinal b-glucuronidase was significantly in- sucrase in duodenum, jejunum and ileum regions of dia- creased in all regions in diabetic control rats when com- betic rats was 6.7-fold, 1.6-fold and 1.6-fold of that in pared with that in the normal control group. The activity normal rats, respectively. The activity of maltase in duo- of b-glucuronidase in duodenum, jejunum and ileum re- denum, jejunum and ileum regions of diabetic rats was gions of diabetic rats was 1.7-fold, 1.5-fold and 1.9-fold 4.1-fold, 4.4-fold and 4.4-fold of that in normal rats, re- of that in normal rats, respectively. Treatment with insulin spectively. Treatment with insulin or berberine resulted in or berberine significantly decreased b-glucuronidase activ- a significant decrease in disaccharidase activities in all ity in all regions of the intestine compared with the dia- three regions of the intestine compared with the diabetic betic group. The intestinal b-glucuronidase activity of in- group. Although the decreasing disaccharidase activity sulin treated diabetic rats had almost recovered to the effect of berberine was not as good as insulin, the ex- same level of normal control rats. perimental data documented the general normalizing ef- fect of berberine treatment on disaccharidase activities. The intestinal maltase activity of insulin treated diabetic Fig. 3: Sucrase activity in the small intestine in different treatment of rats. Fig. 5: b-glucuronidase activity in the small intestine in different treatment Each bar represents the mean Æ S.D., n ¼ 5, for each region of the of rats. Each bar represents the mean Æ S.D., n ¼ 5, for each re- intestine. **Denotes statistical difference compared with normal gion of the intestine. **Denotes statistical difference compared with control rats. (p < 0.01, by ANOVA). DDenotes statistical difference normal control rats. (p < 0.01, by ANOVA). DDenotes statistical compared with diabetic rats. (p < 0.01, by ANOVA) difference compared with diabetic rats. (p < 0.01, by ANOVA) Pharmazie 63 (2008) 5 385 ORIGINAL ARTICLES 3. Discussion small intestine of rats with type 1 diabetes mellitus and type 2 diabetes mellitus was much higher than that in normal rats The results from the present study showed a significant in- (Hoffman et al. 1992; Takenoshita et al. 1998; Dyer et al. crease in the activities of disaccharidases in the intestinal 2002). This might result in an abnormal increase in the mucosa of diabetic rats leading to the observed elevated sucrase, isomaltase and lactase activities in the small intes- glucose level in the blood. The significant increase in ac- tine of diabetic rats. tivities of disaccharidases observed in diabetic rats in this Takenoshita et al. (1998) reported that insulin had a sup- study was consistent with previous reports (Younoszai and pressive effect on the synthesis of the SI complex, pre- Schedl 1972; Nashiro et al. 1992; Murkami and Ikeda sumably by decreasing the transcriptional level of the 1998). The increased levels of disaccharidase activity in gene encoding the complex, in small-intestinal epithelial diabetic rats had been postulated to be a result of hyper- cells. Our report showed that disaccharidase activity was still glycemia (Murakami and Ikeda 1998) and intestinal hyper- decreased 24 h after the last administration of berberine. It plasia (Adachi et al. 2003). Tandon et al. (1975) reported was reported that half-life of of berberine after oral adimi- that insulin had an inhibitory effect on disaccharidase ac- nistration was about 6 h (Lu et al.